The effects of endogenous and dietary estrogens on colonic stem cells

描述(申请人提供)：我们的数据支持这样的假设，即内源性雌激素(E2)或含有雌激素化合物的化学保护性饮食可降低结肠癌发生的风险。这与人体研究表明，暴露在结肠中的雌激素可以防止恶变是一致的。尽管存在与雌激素治疗相关的问题，但饮食中的植物雌激素可能会提供一种合适的替代方案。事实上，流行病学数据表明，含有染料木素(Gen)等植物雌激素的大豆可以降低患结肠癌的风险。关于假定的靶点，结肠的“成年”体细胞干细胞特别令人感兴趣，因为它们维持自我更新，是癌症启动突变的靶细胞。最近的证据表明，正常的肠道干/祖细胞可以启动结肠肿瘤的发生，并推动肿瘤向转移方向发展。不幸的是，到目前为止，内源性和饮食雌激素对肠道干细胞信号的影响还没有确定。由于雌激素化合物可以影响调控结肠干细胞生态位和肿瘤进化的基因/介质，例如P53信号，我们的总体目标是进一步阐明E2和膳食基因如何在不同的恶性转化阶段调节结肠干细胞。基于我们的实验结果，我们提出了两个具体的目标来确定内源性(E2)和饮食雌激素(GEN)如何影响结肠中的多能干细胞。目的1将利用高度特异的干细胞特异性Lgr5-LacZ和Lgr5-EGFP小鼠，定量研究内源性雌激素和饮食来源雌激素在结肠癌发生初期和肿瘤阶段的干细胞数量和时空位置、DNA损伤和结肠癌发生过程中的靶向凋亡。目的利用Lgr5-干细胞靶向p53基因缺失小鼠(Lgr5-EGFP-IRES-creERT2 x p53Flox/Flox)，研究P53在肠道干细胞中介导E2和GEN效应的分子作用。这项拟议的研究具有很高的创新性，将探索饮食中雌激素化合物对结肠多潜能干细胞的生理作用。 公共卫生相关性：流行病学和临床数据表明，食用植物来源的、饮食中的植物雌激素和/或暴露于内源性雌激素可降低女性患结直肠癌的风险。拟议的研究将确定以前未被测试的机制，即饮食中的植物雌激素和内源性雌激素影响结肠中的干细胞群体。从长远来看，这些研究将为开发降低结肠癌风险的新饮食策略提供基础，并可能导致预防结肠癌患者肿瘤复发的新建议。

DESCRIPTION (provided by applicant): Our data support the hypothesis that endogenous estrogen (E2) or a chemoprotective diet containing estrogenic compounds reduce the risk of colon tumor development. This is consistent with human studies demonstrating that exposure to estrogen in the colon protects against malignant transformation. Although there are concerns related to estrogen therapy, dietary phytoestrogens may provide a suitable alternative. Indeed, epidemiological data suggest that soy, containing phytoestrogens such as genistein (Gen), reduces colon cancer risk. With respect to putative targets, "adult" somatic stem cells of the colon are of particular interest because they sustain self-renewal and are target cells for cancer initiating mutations. Recent evidence indicates that normal intestinal stem/progenitor cells can initiate colon tumorigenesis and drive cancer progression towards metastasis. Unfortunately, to date, the effects of endogenous and dietary estrogens on intestinal stem cell signaling has not been determined. Since estrogenic compounds can impact genes/mediators that regulate the colon stem cell niche and tumor evolution, e.g. p53 signature, our overall goal is to further elucidate how E2 and dietary Gen modulate colonic stem cells at distinct stages of malignant transformation. Based on our experimental findings, we propose two specific aims to determine how endogenous (E2) and dietary estrogen (Gen) impact multipotent stem cells in the colon. Aim 1 will use highly novel stem cell specific Lgr5-LacZ and Lgr5-EGFP mice to quantify the number and spatio-temporal location of stem cells, DNA damage and targeted apoptosis in the colonic crypt at the initiation and tumor stages of colon carcinogenesis following exposure to endogenous and diet-derived estrogens. Aim 2 will use Lgr5-stem cell targeted p53 null mice (Lgr5-EGFP-IRES-creERT2 x p53flox/flox) to define the molecular role of p53 in mediating the effects of E2 and Gen in intestinal stem cells. The proposed studies are highly innovative and will explore the physiological actions of dietary estrogenic compounds on multipotent stem cells in the colon. PUBLIC HEALTH RELEVANCE: Epidemiological and clinical data suggest that consumption of plant derived, dietary phytoestrogens and/or exposure to endogenous estrogen reduces the risk of colorectal cancer in women. The proposed studies will define previously untested mechanisms by which dietary phytoestrogens and endogenous estrogen influence stem cell populations in the colon. In the long-term, these studies will provide the basis for developing new dietary strategies for reducing colon cancer risk and may lead to new recommendations for prevention of tumor reoccurrence in colon cancer patients.